The firm Moeller GmbH sells multipole circuit breakers of the type NZM7, which are provided with a connection module on both incoming and outgoing sides, said connection modules having terminal compartments which are isolated from each other and which can be equipped with additional features for different types of connection. Contact straps provided with a through-hole extend from the interior of the circuit breaker into the terminal compartments. To allow connection of round conductors, provision is made for box terminals which can be inserted into the terminal compartments from the front side, and which embrace the contact straps when the connection module is attached to the main housing of the circuit breaker. The box terminals are held by first guide elements extending perpendicular to the front side of the circuit breaker and by a front cover as well as the terminal compartment bottoms facing the bottom wall of the circuit breaker. To allow connection of flat conductors or cable lugs, provision is made for threaded plates which can be inserted into the terminal compartments in a direction toward the terminal side. The threaded plates are clampingly held by second guide elements which are formed on the terminal compartment bottoms and extend parallel to the bottom wall. First terminal screws extend through connection holes of the flat conductors or cable lugs, the through-holes of the contact straps, and tapped holes of the threaded plates, and into through-openings connecting the terminal compartment bottoms to the bottom wall. To allow connection of conductor bars of a busbar adapter to be connected to the circuit breaker on the bottom side, provision is made for terminal sleeves. The cylindrical terminal sleeves extend from the bottom wall into the through-openings, abut the contact straps at one end and, at the other end, they extend from the bottom wall to connection holes of the conductor bars. Second terminal screws extend through the through-holes of the contact straps and through the terminal sleeves, and into female threads of the conductor bars. A cover has access openings through which the clamping screws of the box terminals, or the first or second terminal screws can be operated using a screw tool. In order to provide the required clearance and creepage distances between the terminal compartments, three-pole circuit breakers are provided with six individual sealing plugs, and four-pole circuit breakers are provided with eight individual sealing plugs, said sealing plugs having to be inserted from the bottom wall into the through-openings when the connection is via box terminals or threaded plates.